Memory leak

[crysan]

Hi!

When using this code

Sql2o sql2o = new Sql2o("jdbc:mysql://127.0.0.1:3306/db?autoReconnect=true&failOverReadOnly=false&useUnicode=true&useJDBCCompliantTimezoneShift=true&useLegacyDatetimeCode=false&serverTimezone=UTC", "root", "");

		while (true) {
			List<Map<String, Object>> result_ = null;
			try (Connection con = sql2o.open()) {
				result_ = con.createQuery("SELECT * FROM tbltasks WHERE end_date=:end_date LIMIT 1").addParameter("end_date", "1970-01-01 00:00:00").executeAndFetchTable().asList();
				con.close();
			}

			for (Map<String, Object> a_ : result_) {
				int task_id = (int) a_.get("id");
				String type = (String) a_.get("type");
				String content = (String) a_.get("content");

				...
			}
		}

There is a big memory leak. In 1 hour the loss reaches 4 GB.
What to do?
Thank!

[zapodot]

Hi! I suppose that this code is running continuously as you have a endless loop in your code:
while(true)
It also seems like the result_ variable is reused during the loop. Is that ever cleaned up? If not that may be the issue here.. Secondly, there is no need to call con.close() as you already are using a try with resources statement which will close the connection after use.

Without further context it is not easy to see how the SQL2O library may have caused this memory leak

[crysan]

Thanks for the answer!

That's right, the program should work endlessly and check the contents of the database.
Redid the program only for this code

		List<Map<String, Object>> result_ = null;
		while (true) {
			try (Connection con = sql2o.open()) {
				result_ = con.createQuery("SELECT * FROM tbltasks WHERE end_date=:end_date LIMIT 1").addParameter("end_date", "1970-01-01 00:00:00").executeAndFetchTable().asList();
				//con.close();
			}

			for (Map<String, Object> a_ : result_) {
				int task_id = (int) a_.get("id");
				String type = (String) a_.get("type");
				String content = (String) a_.get("content");
			}
			
			result_.clear();
		}

the problem is not solved.
Memory leak remained.

[zapodot]

Have you tried to run some kind of performance leak tool such as https://www.eclipse.org/mat/ to find out which objects are leaking? Another thought: why do you first retrieve the results to a list first using executeAndFetchTable and then iterate that same list. Why not map the results directly using either a ResultHandler or by creating a POJO? That would mean that all intermediary objects would be short-lived and thus would be eligible for garbage collection.

…

On Tue, Dec 4, 2018 at 2:15 AM Sani ***@***.***> wrote: Thanks for the answer! That's right, the program should work endlessly and check the contents of the database. Redid the program only for this code List<Map<String, Object>> result_ = null; while (true) { try (Connection con = sql2o.open()) { result_ = con.createQuery("SELECT * FROM tbltasks WHERE end_date=:end_date LIMIT 1").addParameter("end_date", "1970-01-01 00:00:00").executeAndFetchTable().asList(); con.close(); } for (Map<String, Object> a_ : result_) { int task_id = (int) a_.get("id"); String type = (String) a_.get("type"); String content = (String) a_.get("content"); } result_.clear(); } the problem is not solved. Memory leak remained. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#310 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AAhqkXdVVz7rjG0L47mzEdZoHUuJc0h_ks5u1cyYgaJpZM4YxOnO> .